here is jon karl. >> reporter: inside this unmarked building, through the empty lobby past the small warning sign, across the second lobby, up several floors, we find the secret place that the government borrows unthinkable sums of money almost every day. it looks like we could be in any office building anywhere in america except for the old war bond posters on the wall. the only indication of what is happening here and where we are, is this tiny sign, auction room. hard to believe but what happens inside this room is the difference between the government operating for another day or turning the lights out. >> this is how we finance the u.s. government where it happens. >> reporter: right here in this room? >> right here. >> reporter: assistant treasury secretary mary miller the most powerful woman you never heard of. three times a year she supervises auctions finding out if the world is willing to loan the government more by buying ious, treasury bonds. this auction will last 90 minutes and bring in $28 billion, enough to fund the entire federal government, everything from the penta